The sister of Celtics guard Isaiah Thomas was killed in a single-car accident Saturday morning.

Chyna J. Thomas, the 22-year-old sister of the 2016-17 NBA MVP candidate, was driving her 1998 Toyota Camry when she drifted off the road and hit a Jersey barrier and then a sign post, according to Washington State Patrol officials. The accident occurred around 5 a.m. Saturday on I-5 in Isaiah Thomas' home state of Washington.

Police said Chyna Thomas was not wearing a seatbelt.

The Celtics confirmed the woman's identity in a statement Saturday evening.

"We are terribly saddened by the tragic loss of Chyna Thomas. The thoughts and prayers of the entire Celtics organization are with Isaiah and his family."

The Celtics have the No. 1 seed in the Eastern Conference and will play the No. 8 seed Chicago Bulls in the first round of the playoffs Sunday night at 6:30 p.m. at home.